Where … at (Where was he at?) and where … to (Where is this leading to?) are often criticized as redundant because neither at nor to adds anything to the meaning of where, and sentences like the preceding ones are perfectly clear and standard without the final at or to. This criticism does not apply to where … from, which is fully standard: Where does the money come from? The constructions where … at and where … to occur in the speech of educated people but are rare in formal speech and edited writing.

(subordinating) in the place at which: where we live it's always raining

noun

4.

(usually pl) a question as to the position, direction, or destination of something

Usage note

It was formerly considered incorrect to use where as a substitute for in which after a noun which did not refer to a place or position, but this use has now become acceptable: we now have a situation where/in which no further action is needed

Word Origin

Old English hwǣr, hwār(a); related to Old Frisian hwēr, Old Saxon, Old High German hwār, Old Norse, Gothic hvar